1. Field of the Invention
This invention generally relates to isolating input/output adapter addressing domains in a data processing system. More specifically, the invention relates to isolating input/output adapter addressing domains in a logically partitioned data processing system implementing HyperTransport. The term “isolation”, as used herein, refers to verifying that an I/O adapter actually owns or has the right to access particular system memory locations for which it is requesting access. Thus, if an I/O adapter is properly isolated to a preassigned memory space, it will only request access to that area of memory.
2. Background Art
In a logically partitioned data processing system, multiple operating systems or multiple copies of a single operating system are run on a single data processing system platform. Each operating system or operating system copy executing within the data processing system is assigned to a different logical partition (“LPAR”), and each partition is allocated a non-overlapping subset of the resources of the platform. Thus, each operating system or operating system copy directly controls a distinct set of allocatable resources within the platform.
Among the platform resources that may be allocated to different partitions are processors or time slices of processors, regions of system memory, and I/O Adapters (“IOAs”) or parts of IOAs. Thus, different regions of system memory and different IOAs or parts of IOAs may be assigned to different partitions, i.e. each IOA is “owned” by a partition. In such an environment, it is important that the platform provide a mechanism to enable IOAs or parts of IOAs to obtain access to all the physical memory that they require to properly service the partition or partitions to which they have been assigned; while, at the same time prevent IOAs or parts of IOAs from obtaining access to physical memory that has not been allocated to their associated partitions.
In a logically partitioned data processing system, various communication technologies may be used to link together the electronic devices of the system via both physical media and wirelessly. Some communication technologies interface a pair of devices, other communication technologies interface small groups of devices, and still other communication technologies interface large groups of devices.
One relatively new communication technology for coupling relatively small groups of devices is the HyperTransport (HT) technology. The HT Standard sets forth definitions for a high-speed, low-latency protocol that can interface with today's buses such as AGP, Peripheral component interconnect (“PCI”), 1394, USB 2.0, and 1 Gbit Ethernet as well as next generation buses including AGP 8×, Infiniband, PCI-X, PCI 3.0, PCIe, and 10 Gbit Ethernet. HT interconnects provide high-speed data links between coupled devices. Most HT enabled devices include at least a pair of HT ports so that HT enabled devices may be daisy-chained. In an HT chain or fabric, each coupled device may communicate with each other coupled device using appropriate addressing and control. Examples of devices that may be HT chained include packet data routers, server computers, data storage devices, and other computer peripheral devices.
HT thus offers many important advantages. Using HyperTransport attached I/O bridges in a logically partitioned data processing system, however, requires a way of isolating IOA direct memory access (“DMA”) and interrupt requests to the owning LPAR.
Importantly, one LPAR could affect another through an IOA. With logical partitions, an OS in one partition cannot communicate with an OS in another partition through an IOA. For example, one OS may send commands and addresses to an IOA, and the IOA would perform DMA using these addresses. There is no mechanism to check the addresses that are provided by the OS to the IOA. Instead, the BAR/limit (and later, the translation validation table (TVT)) verifies the address when it is presented to the host by the IOA.